Human joints have a type of cartilage known as intra-articular fibrocartilage. Intra-articular fibrocartilage can be present in the form of a discus articularis, that is, as a plate or ring of fibrocartilage in the joint capsule separating the joint surfaces (articular cartilage) of the bones of the joint. Such fibrocartilage is present, for example, in the temporomandibular joint, between vertebrae, and in the knee joint. In the knee joint, the intra-articular fibrocartilage comprises the meniscus, a crescent-shaped or semi-lunar-shaped disc of tissue that is located between the femoral condyles and the tibial plateau. The meniscus primarily functions as a shock absorber, absorbing the shock of compressive and shear forces in the knee. The meniscus also provides a substantially frictionless surface for articulation of the knee joint.
When cartilage tissue is no longer healthy, there can be debilitating pain in the joint. Cartilage health can be adversely affected by disease, aging, or trauma. The adverse effects of disease, aging and trauma can be in the form of a tear in the cartilage or in the form of a breakdown of the cartilage matrix.
In the knee, the meniscus is frequently damaged in twisting injuries. It is also damaged with repetitive impact over time. Meniscus degeneration can also occur by aging; as a person ages, the meniscus can become soft in places, so that even common motions like squatting can cause meniscal tears.
Common surgical procedures for treating meniscal damage include tear repairs and menisectomies. A tear repair is most commonly performed when the tear is a clean longitudinal vertical lesion in the vascular red zone of the meniscus. The basic strategy is to stabilize the tear by limiting or eliminating radial separation of the faces of the tear when the meniscus is load bearing. Many devices and surgical procedures exist for repairing meniscal tears by approximating the faces of the meniscus at the tear. Examples of such devices and procedures are disclosed in the following U.S. Pat. Nos. 6,319,271; 6,306,159; 6,306,156; 6,293,961; 6,156,044; 6,152,935; 6,056,778; 5,993,475; 5,980,524; 5,702,462; 5,569,252; 5,374,268; 5,320,633; and 4,873,976.
Menisectomies involve the surgical removal of part of the meniscus. Such procedures have generally been performed in cases of radial tears, horizontal tears, vertical longitudinal tears outside the vascular zone, complex tears, or defibrillation. Although menisectomies provide immediate relief to the patient, in the long term the absence of part of the meniscus can cause cartilage wear on the condylar surface, eventually leading to arthritic conditions in the joint.
Generally, an orthopaedic surgeon has several options in gaining access to damaged intra-articular fibrocartilage: a fully open arthrotomy, a mini-arthrotomy and the creation of several small portals for use in arthroscopy. In a fully open arthrotomy, a relatively large incision is made to expose the joint. In a mini-arthrotomy, a smaller incision is made to expose less of the joint; in knee surgery, the patella would not typically be subluxated in a mini-arthrotomy of the knee. In arthroscopy, small incisions are made at the affected joint to form portals for the insertion of instruments, including a small lens and lighting system (an arthroscope). The arthroscope is connected to a viewing device, such as a television camera to allow the surgeon to see the interior of the joint. Other instruments are inserted through other portals to perform a variety of tasks. For example, the surgical instrument may include an implement for manipulating native tissue (for example, tissue grasping, tissue cutting, bone abrading).
For faster healing, minimally invasive surgical procedures, such as arthroscopic procedures and mini-arthrotomies, are preferred. Typical surgical instruments used in arthroscopic procedures include rongeurs, such as the Kerrison rongeur, punch forceps, basket forceps, suction punches and cup curet, for example. Examples of arthroscopic instruments are described and illustrated in O'Cornor's Textbook of Arthroscopic Surgery, 2nd ed., 1992, Chapter 19.